Magnetic Resonance Spectroscopic Evaluation of Brain Tissue Metabolism After Irradiation for Pediatric Brain Tumors in L

The aim of our study was to evaluate the metabolic profile of brain tissue of two long-term survivors of childhood brain tumors.

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ract  Objective  The aim of our study was to evaluate the metabolic profile of brain tissue of two long-term survivors of childhood brain tumors. Materials  Two males who were 25 and 33 years old at the time of examination and had been irradiated for brain tumors at the age of 17 and 13 years respectively. The first subject had been operated on radically for medulloblastoma and received craniospinal axis irradiation composed of a whole brain radiotherapy with boost to the posterior fossa (total dose (TD) = 59.4 Gy in 33 fractions) and spinal canal irradiation (TD = 30 Gy in 20 fractions) according to the protocol at the time of treatment. The second subject had previously received whole brain irradiation (TD = 45 Gy in 19 fractions) because of inoperable central region tumor of unknown histology. Methods  Short echo-time (TE = 30ms) point-resolved spectra were obtained using a 2 T magnet. Ratios of N-acetylaspartate (NAA), choline (Cho), myo-inositol (mI), lactate (Lac) and lipids (Lip) signal intensities were calculated using the creatine (Cr) signal as an internal reference. The spectra were acquired both from the tumor bed area and uninvolved brain tissue in the first subject, and from uninvolved brain areas of frontal and occipital lobes in the second subject. Results  In both cases, MRS examination revealed ratios of NAA/Cr, Cho/Cr and mI/Cr within normal range in most spectra. Nevertheless, a slight elevation of Lac/Cr (2.47 and 1.05) and a more pronounced elevation of Lip/Cr proportions (45.77 and 3.97 respectively, in uninvolved sites) were detected in both patients.

S. Blamek (), and J. Wydman´ski Department of Radiotherapy, Maria Skłodowska-Curie Memorial Cancer Center and Institute of Oncology, Gliwice Branchul, Wybrzeże Armii Krajowej 15, Gliwice 44-100, Poland e-mail: [email protected] M. Sokół, Ł. Matulewicz, and Ł. Boguszewicz Department of Medical Physics, Maria Skłodowska-Curie Memorial Cancer Center and Institute of Oncology, Gliwice Branchul, Wybrzeże Armii Krajowej 15, Gliwice 44-101, Poland

Conclusions  Metabolic parameters correlated with neuronal function (NAA/Cr) and cell membrane metabolites turnover (Cho/Cr) seem to recover to normal values in long-term survivors of brain tumors. Lac/Cr and Lip/Cr proportions could be considered parameters indicating permanent radiation-induced brain damage; however, this proposal requires further investigation. Keywords  Magnetic resonance spectroscopy • pediatric brain tumors • long-term survivors • radiotherapy • adverse effects

Introduction Management of brain tumors in children requires an aggressive therapy usually composed of surgery, chemotherapy, and irradiation. Late sequelae of this regiment are attracting growing attention because of the increasing number of long-term survivors of childhood brain cancer. Most reports concentrate on white matter damage, cognitive impairment, and results of neuropsychological testing (2,10,11). The assessment of the metabolic profile of the brain has not been so intensively investigated, and available reports de